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Meiourogonyaulax psora
Meiourogonyaulax psora Davey and Verdier, 1974
Originally (and now) Meiourogonyaulax, subsequently Lithodinia. This species is here retained in Meiourogonyaulax following the retention of the genus by Riding and Helby (2001d, p.81,83).
Gocht, 1976, transferred this species to Lithodinia Eisenack, 1935. Stover and Evitt, 1978, retained it in Meiourogonyaulax. Williams et al., 1993, agreed with Gocht, 1976.
Holotype: Davey and Verdier, 1974, pl.92, fig.9
Locus typicus: La Bedoule, SE France
Stratum typicum: Early Aptian (Bedoulian)
Original diagnosis: Davey and Verdier, 1974, p.634
The cyst is subcircular to slightly angular in outline. The cyst wall is relatively thick and is characterized by a variable surface ornamentation consisting of isolated tubercles to low irregular vermicular ridges. The sutural ridges are low and are difficult to discern except at the margins of the cyst, they are formed by the coalescence of aligned tubercles and/or broad, flat-topped processes. The cingulum, which is narrow, is displaced by approximately one cingular width along the sulcus. The latter broadens on the hypotract and has a noticeable deep, centrally placed longitudinal groove. The apical archaeopyle is angular and the operculum sometimes remains attached.
Description: Davey and Verdier, 1974, p.634
On one specimen a low (5 Ám), conical, membranous apical horn is present. The remaining complete specimens only possess slight apical prominences which are indistinguishable from the other angularities of the cyst outline. The thick (up to 3 Ám) cyst wall is densely warty and rugulate. The sutural ridges, which are often discontinuous, are of similar height (up to 5 Ám) to this ornamentation and thus are difficult to locate. Only on the cyst margin is it possible to see that the ridges are sometimes composed of long broad processes which anastomose distally. The cingulum is narrow (3-5 Ám in width), does not appear to be tabulate, and sometimes forms ledges on the cyst circumference.
Affinities:
Davey and Verdier, 1974, p.634: M. psoros is easily distinguished from all oter species of Meiourogonyaulax by its distinctive rugulate ornamentation and low sutural crests.
Originally (and now) Meiourogonyaulax, subsequently Lithodinia. This species is here retained in Meiourogonyaulax following the retention of the genus by Riding and Helby (2001d, p.81,83).
Gocht, 1976, transferred this species to Lithodinia Eisenack, 1935. Stover and Evitt, 1978, retained it in Meiourogonyaulax. Williams et al., 1993, agreed with Gocht, 1976.
Holotype: Davey and Verdier, 1974, pl.92, fig.9
Locus typicus: La Bedoule, SE France
Stratum typicum: Early Aptian (Bedoulian)
Original diagnosis: Davey and Verdier, 1974, p.634
The cyst is subcircular to slightly angular in outline. The cyst wall is relatively thick and is characterized by a variable surface ornamentation consisting of isolated tubercles to low irregular vermicular ridges. The sutural ridges are low and are difficult to discern except at the margins of the cyst, they are formed by the coalescence of aligned tubercles and/or broad, flat-topped processes. The cingulum, which is narrow, is displaced by approximately one cingular width along the sulcus. The latter broadens on the hypotract and has a noticeable deep, centrally placed longitudinal groove. The apical archaeopyle is angular and the operculum sometimes remains attached.
Description: Davey and Verdier, 1974, p.634
On one specimen a low (5 Ám), conical, membranous apical horn is present. The remaining complete specimens only possess slight apical prominences which are indistinguishable from the other angularities of the cyst outline. The thick (up to 3 Ám) cyst wall is densely warty and rugulate. The sutural ridges, which are often discontinuous, are of similar height (up to 5 Ám) to this ornamentation and thus are difficult to locate. Only on the cyst margin is it possible to see that the ridges are sometimes composed of long broad processes which anastomose distally. The cingulum is narrow (3-5 Ám in width), does not appear to be tabulate, and sometimes forms ledges on the cyst circumference.
Affinities:
Davey and Verdier, 1974, p.634: M. psoros is easily distinguished from all oter species of Meiourogonyaulax by its distinctive rugulate ornamentation and low sutural crests.